When an air-fuel mixture is combusted in an engine combustion chamber, a small portion of the combusted gas may enter the engine crankcase through the piston rings. This gas is referred to as blow-by gas. To prevent this untreated gas from being directly vented into the atmosphere, a crankcase ventilation system is provided between the higher pressure crankcase and the lower pressure intake manifold to allow the blow-by gas to flow from the crankcase into the intake manifold and be mixed with fresh air. From here, the gas may be re-inducted into the combustion chamber for re-combustion.
Engine lubrication oil used to lubricate moving parts of the engine is present in the crankcase during normal engine operation. The high pressure in the crankcase causes some of the lubricating oil to be suspended in a mist form. This oil mist can then mix with the blow-by gas and be returned to the intake manifold for combustion via a communication passage. However, combustion of the oil may cause the net oil consumption to increase, as well as degrade engine emission quality. To address these issues, oil separators have been developed to separate the oil content from the blow-by gas containing the oil mist. After separation, the oil is returned to the engine lubricating system while the blow-by gas is returned to the engine intake system.
One such oil separator is disclosed by Nonaka et al. in U.S. Pat. No. 7,117,858 wherein the separator is provided in combination with a cylinder head cover of an internal combustion engine. The separator includes a separator cover with a partition wall to define a first and second separator chamber on opposite sides of the wall, as well as a plurality of drain pipes to drain oil droplets from the separator into a valve operating chamber. In '858, the configuration of the separator causes the flow rate of the blow-by gas to be lowered in the separator chambers to thereby allow the oil to separate by its own weight. The cover further includes a plurality of projection walls projecting from the inner surface of the cover for separating oil from the mist by impaction.
However, the inventors have recognized several issues with such an oil separator. As one example, the distinct chambers and the related partition walls consume a significant amount of the limited space available above the cylinder head in the engine compartment. For example, in a turbocharged V-6 engine operating with a direct injection of gasoline, the configuration of the engine may result in very limited space, particularly above the cylinder heads on the left hand bank. The spatial constraints may not allow an oil separator with the configuration of '858 to be mounted. As such, this may lead to a reduction in oil separation efficiency in the engine, thereby degrading overall engine oil consumption and exhaust emission levels.
Thus in one example, the above issues may be addressed by an oil separator mounted on a cylinder head of an internal combustion engine, to separate oil mist from blow-by gas. The oil separator may comprise a camcover configured to be mounted on a cylinder head and a baffle positioned between the camcover and the cylinder head. The baffle may include at least a first and a second baffle plate, the first baffle plate including a first through-hole on a first face of the first baffle plate, the second baffle plate including a second through-hole on a second face of the second baffle plate. The first and second faces may be positioned opposite one another, and may be offset such that the first and second through-holes are not fully overlapping. The positioning of the first and second faces and the degree of overlap between the through-holes may be adjusted responsive to the particle size of the oil. In some embodiments, the through-holes may be offset such that they are partially overlapping. In other embodiments, the through-holes may be offset such that there may be substantially no overlap, thereby causing oil separation by multiple and repetitive impacts.
In this way, multiple impaction stationary baffles may be incorporated into an oil separator to meet the high oil challenge in an engine. In one particular example with similarly shaped baffles, manufacturing costs may be reduced. Manufacturing costs may also be reduced by further molding the whole baffle arrangement using a single plastic mold. And, in another example in which the separator is configured to enable oil separated at the baffles to drip directly onto the camshaft or onto cam caps, the need for oil drain valves and/or oil drain paths may be averted or reduced, thereby allowing the separator to work more efficiently within the spatial constraints.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.